SUMMARY Evidence for retroviral infection in general and human immunodeficiency virus (HIV) infection in particular was sought in freshly isolated peripheral blood T cells, B cells, and monocyte-macrophages from patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) and also in T cell and B cell lines established from the same source. Similar cells isolated from rheumatoid synovial membrane were also examined. The strategy used for the detection of virus was cocultivation with susceptible cell lines looking for syncytia formation, reverse transcriptase production, and nucleic acid hybridisation with HIV cDNA probes. No evidence for infection was obtained.